Mechanical steering transmission unit

ABSTRACT

The present invention concerns a mechanical steering transmission unit comprising an input drive shaft and two output driven shafts that can revolve in the same or opposite direction at the same speed.

[0001] The present application for industrial patent concerns amechanical transmission unit especially designed for vehicles running onwheels or belts. This unit will allow the vehicle to turn around animaginary point placed between the couple of belts or wheels withoutstopping.

[0002] Since the mechanism of the invention was developed with thespecific aim of solving a typical problem of caterpillars, henceforththe present description will refer to this type of vehicles. However,any vehicle running on four wheels and machines in general can equallybenefit from using the mechanism.

[0003] As it is known, the easiest way to make a caterpillar turn is tobrake the belt on the internal side of the curve and block it downcompletely. This technique is employed to make the vehicle turn onitself using one of the belts as pivots.

[0004] It is evident, however, that using this technique it will beimpossible to make the caterpillar turn around an imaginary point placedbetween the lateral couple of belts. As it is often the case for somemodels of highly sophisticated combat tanks, when such a performance isrequired, the tanks are equipped with special hydraulic transmissionunits, which employ two hydraulic motors (one for each belt). Whenneeded, the motors start revolving in opposite direction. In this waythe center of curvature of the vehicle falls inside the lateral coupleof belts.

[0005] It must be stressed, however, that in these cases thisperformance (that is to make the motors run in the opposite direction)cannot be achieved without having previously stopped the run of thevehicle. This means that it is not possible to make the vehicle turn onitself without previously stopping its straight run.

[0006] The aim of the invention is to invent a mechanical transmissionunit with two output driven shafts that, when needed, will allow thecounter-rotation of the two output shafts. If the aforementioned shaftsdrive the belts of the caterpillar, a rotation of the caterpillar onitself will correspond to this counter-rotation.

[0007] An additional aim of the invention is to develop a mechanicaltransmission unit with two output driven shafts that will allow thecounter-rotation of the two output shafts without stopping them, whenneeded.

[0008] In order to avoid any misunderstanding, the description of thetransmission unit of the invention will proceed with reference to theenclosed drawing. However, the drawing has the only purpose ofillustrating the invention and is not binding in any way. Therefore,FIG. 1 only shows a possible representation of the transmission unit ofthe invention.

[0009] With reference to the aforementioned figure, the transmissionunit of the invention includes a drive shaft (1) that, by means of acouple of bevel gears (2 a and 2 b), drives a driven shaft (3) at whoseends two identical differential gears (5) are mounted, from which twodriven shafts (6 and 7) originate. If the unit is mounted in amotor-vehicle, the driven shafts (6 and 7) can drive the belts or wheelsof the vehicle.

[0010] A cogwheel has been splined to the drive shaft (1). The cogwheel(8) gears with a couple of cogwheels (9 and 10). The cogwheels (9 and10) lie opposite the cogwheel (8), are identical to cogwheel (8) andsplined to the driven shafts (11 and 12), which are parallel and lieopposite the drive shaft (1).

[0011] The two driven shafts (11 and 12) are linked to two differentialgears (5) by means of two couples of bevel gears (13 a and 13 b) and (14a and 14 b) that lie near the opposite sides of the aforementionedcouple of bevel gears (2 a and 2 b).

[0012] It is important to stress that the three couples of bevel gears(2 a and 2 b), (13 a and 13 b) and (14 a and 14 b) are identical.

[0013] Since the driven shafts (11 and 12) revolve in the oppositedirection of the drive shaft (1), the bevel gear (2 b) splined to theshaft (3) lies upside down with reference to the two bevel gears (13 aand 14 b) in order to make the revolving direction of the shaft (3) thesame as the other two shafts (6 and 7).

[0014] Finally, it must be stressed that two identical hydraulic units(15) are mounted on each of the shafts (11 and 12) and drive twoantithetical clutches (16 a and 16 b). The former (16 a) controlstransmission of motion from cogwheels (9 and 10) to the driven shafts(11 and 12); whereas the latter (16 b) prevents the free rotation of theframe (17) and driven shafts (11 and 12), making them revolve in thesame direction.

[0015] Following is a description of how the transmission unit of theinvention will perform when mounted on a motor-vehicle.

[0016] When the vehicle runs in straight direction, the clutches (16 a)are geared in, whereas clutches (16 b) are not In this case the shafts(11 and 12) revolve with the same number of revolutions as the driveshaft (1). In addition to this, since the differential gears (5) are notperforming because the three bevel gears (2 b, 13 b and 14 b) revolvewith the same number of revolutions, the output shafts (6 and 7) revolvein the same direction and with the same number of revolutions as thecentral shaft (2).

[0017] When the vehicle has to turn on itself around an imaginaryvertical axis placed between its opposite couple of belts or wheels, oneof the two hydraulic units (15) must be started. This will ungear thegeared clutch (16 a) and will gear the proper clutch (16 b). In thisway, the driven shaft (11 and 12)—depending on the hydraulic unit thathas been started (15)—will stop, since it is no longer driven by itscogwheel (9 or 10) and it is blocked to the frame (17) by clutch (16 b).

[0018] Consequently, the differential gear (5) of one of the two bevelgears (13 a and 14 a) that cannot revolve because its shaft (11 or 12)has ceased to revolve will start to perform.

[0019] The performance of one of the two differential gears (5) producesa reversal in the revolution direction of the two output shafts (6 and7), which, however, continue on revolving with the same number ofrevolutions.

[0020] It appears now evident how the use of the invention makes itpossible to make the vehicle switch from running straight to turning onitself without having to stop the vehicle to switch from a mode(straight run) to the other (turning).

[0021] Finally, it is important to stress that, by suitably acting onthe hydraulic units (15), it is also possible to determine the variationin the turning direction of the vehicle and the number of revolutions ofthe output shafts (6 and 7), thus changing the vehicle's turning circle.

1. A mechanical transmission unit, having an input drive shaft (1) andtwo output driven shafts (6 and 7) that is characterised by the factthat is consists of: a couple of bevel gears (2 a and 2 b): the formeris splined to the drive shaft (1), whereas the latter is splined to adriven shaft (3) that is at right angle to the drive shaft (1); at theends of the shaft (1) two identical differential units (5) areinstalled, from which the aforementioned shafts (6 and 7) originate; acogwheel (8) that is splined to the drive shaft (1) and gears with acouple of cogwheels (9 and 10) that are identical to the cogwheel (8),each of which is splined to its driven shaft (11 and 12), which areparallel and whose opposite sides lie near the shaft (1). two couples ofbevel gears (13 a and 13 b) and (14 a and 14 b, which lie near theopposite sides of the aforementioned bevel gears (2 a and 2 b) and areused to link the differential gears (5) to their driven shafts (11 and12); two identical hydraulic units (15) respectively mounted on thedriven shafts (11 and 12), each of them used to start two antitheticalclutches (16 a and 16 b); the former (16 a) controls transmission ofmotion from cogwheels (9 and 10) to their respective driven shafts (11and 12); whereas the latter (16 b) prevents the free rotation of theframe (17) and driven shafts (11 and 12), making them revolve in thesame direction; it is also being provided that: the three couples ofbevel gears (2 a and 2 b; 13 a and 13 b; 14 a and 14 b) are perfectlyidentical; the bevel gear (2 b) is splined to the driven shaft (3) andlies upside down with reference to the two bevel gears (13 a and 14 b).2. A transmission unit according to the previous claim, characterised bythe fact that the output shafts (6 and 7) are parallel and coaxial.